Expansion of tubular elements finds application in various fields of technology including, for example, the production of hydrocarbon fluid from a wellbore formed in an earth formation. Wellbores are generally provided with one or more casings or liners to provide stability to the wellbore wall, and/or to provide zonal isolation between different earth formation layers. The terms “casing” and “liner” normally refer to wellbore tubulars for supporting and stabilising the wellbore wall, whereby it is generally understood that a casing extends from a downhole location to surface, whereas a liner does not fully extend to surface. However, in this specification the terms “casing” and “liner” are used interchangeably and without intended distinction.
In conventional wellbore construction, several casings are set at different depth intervals, and in a nested arrangement. Each subsequent casing has to be lowered through the previous casing and therefore must have a smaller diameter than the previous casing. As a result, the available wellbore diameter for oil and gas production decreases with depth. To alleviate this drawback, it has been practiced to radially expand wellbore tubulars after lowering into the wellbore. Such expanded tubular element is, for example, an expanded casing section or an expanded clad against a previously installed existing casing. If each casing section is expanded to about the same diameter, the available wellbore diameter remains substantially constant along (a portion of) its depth, as opposed to the conventional, nested, arrangement whereby the available wellbore diameter decreases with depth.
EP-044706-A2 discloses a method of radially expanding a tubular element by eversion of an inner tube to form an outer tube around a portion of the inner tube, the tubes being interconnected at their respective forward ends to present a rollover area capable of being moved forwardly. The rollover area is induced to move forward by pumping driving fluid into the annular space between the inner and outer tubes. As the tubular element expands to a larger diameter, the wall stretches in circumferential direction during the eversion process. Therefore the bending radius of the wall in the rollover area does not only depend on the resistance to bending of the wall, but also on the resistance to stretching of the wall in circumferential direction. Such resistance to stretching tends to reduce the diameter of the expanded section, and thereby tends to reduce the bending radius of the wall in the rollover area.
Due to such relatively small bending radius, the wall is subjected to relatively high strains, thereby leading to an increased risk of damage to the wall during the eversion process.
It is therefore an object of the invention to provide an improved method of radially expanding a tubular element, which overcomes the drawbacks of the prior art.